Inertial Sensor Movable Element Opening Ratio Design

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing inertial sensors face challenges in achieving high detection sensitivity while maintaining desired frequency characteristics due to the reduction in capacitance caused by through holes across the movable element, leading to decreased acceleration detection sensitivity.

Innovation Solution

The inertial sensor design includes a movable element with symmetrical and asymmetrical sections, where the first movable section has a greater rotational moment than the second, and the use of dummy electrodes with the same potential as the movable element to suppress electrostatic attraction, along with strategically placed openings to reduce air resistance-induced damping, thereby increasing capacitance and sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a plurality of through holes are uniformly formed across the entire region of the movable element to reduce air resistance, then damping is suppressed for desired frequency characteristics, but the area where the movable section faces the detection electrode is reduced, resulting in decreased capacitance and acceleration detection sensitivity

Engineering Contradiction:

Improvefrequency characteristicsVSAvoidacceleration detection sensitivity

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The movable element is divided into different regions with different opening ratios: the first region (overlapping with detection electrode) has a smaller opening ratio to maintain capacitance and sensitivity, while the second region (overlapping with dummy electrode) has a larger opening ratio to reduce air resistance and damping. This local differentiation resolves the contradiction by optimizing each region for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The movable element is segmented into multiple regions with different opening characteristics. The first region maintains structural integrity and capacitance for sensitivity, while the second region provides air resistance reduction for frequency characteristics. This segmentation allows simultaneous optimization of both contradictory requirements.

Inventive Principle:

Principle #1Segmentation

2Loss of energy

If through holes are formed to reduce air resistance, then damping is reduced, but the capacitance between movable sections and detection electrodes decreases

Engineering Contradiction:

ImprovedampingVSAvoidcapacitance

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

Different regions of the movable element have different opening ratios optimized for their specific functions: the first region prioritizes capacitance maintenance for measurement precision, while the second region prioritizes air resistance reduction for energy loss minimization.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Dummy electrodes are introduced as intermediary elements that interact with the second region of the movable element. These dummy electrodes create capacitance in the region with larger openings, allowing air resistance reduction without sacrificing overall capacitance, thus mediating between the contradictory requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration enhances detection sensitivity while ensuring a desired frequency band, reducing unnecessary electrostatic attraction and damping, and effectively suppressing unwanted vibrations, resulting in improved acceleration detection capabilities.

Implementation Method 1

a movable element that swings around a swing axis extending along the axis Y

Methodology Applied

Scientific EffectInertia: Inertia

Implementation Method 2

the capacitance between the first movable section and the first detection electrode and the capacitance between the second movable section and the second detection electrode change accordingly

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

to reduce air resistance that occurs when the movable element swings to suppress damping of the movable element

Methodology Applied

Scientific EffectAir resistance: Drag

Implementation Method 4

the use of dummy electrodes with the same potential as the movable element to suppress electrostatic attraction

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Data Source

PatentUS11454645B2Inertial sensor, electronic instrument, and vehicle

Publication Date: 2022.09.27 SEIKO EPSON CORP

AI summary

An inertial sensor includes a movable element including a first movable section and a second movable section, a first detection electrode, and a first dummy electrode. The first movable section has a first section, a second section that is farther from the swing axis than the first section, and a third section disposed between the first section and second section. The first section of the first movable section has a first opening and the third section of the first movable section has a second opening. An opening ratio of the first opening to the first section of the first movable section is smaller than an opening ratio of the second opening to the third section of the first movable section.